Discontinuous reception (DRX) is a technique used in wireless communication networks to conserve the battery power of mobile devices. Because data traffic in wireless communication networks is often bursty, with short periods of activity followed by long periods of inactivity, the mobile device may turn its receiver off to conserve battery power during periods of inactivity and turn its receiver on at periodic intervals to monitor the Physical Downlink Control Channel (PDCCH) for uplink grants and downlink transmissions. DRX can result in significant power savings for the mobile device and thus longer battery life.
The network may configure a dedicated connection for a mobile device to employ DRX depending on the capabilities of the mobile device and power preferences. A number of configuration parameters, referred to herein as DRX parameters, are used to configure DRX operation. The DRX parameters, among other things, define a DRX cycle for use when a mobile device is in DRX mode, In Long Term Evolution (LTE), both a short DRX cycle and long DRX cycle may be defined. The parameters shortDRX-Cycle and longDRX-Cycle define the length in subframes of the short and long DRX cycles respectively. The onDuration parameter specifies the number of PDCCH subframes at the beginning of each DRX cycle that the receiver in the mobile device is turned on to monitor the PDCCH (the DRX on duration) before the receiver is turned off. The same onDuration parameter is typically used for both short and long DRX cycles. Other important DRX parameters defined in LTE include drxStartOffset that specifies the PDCCH subframe at which the DRX cycle starts, drx-Inactivity-Timer that specifies the number of consecutive PDCCH subframes that the mobile device should remain active after successfully decoding a PDCCH indicating a new uplink (UL) of downlink (DL) transmission, and drx-Retransmission Timer that specifies the maximum number of consecutive PDCCH-subframes that the mobile device should monitor when a retransmission on the downlink is expected by the mobile device.
There is no single DRX configuration that is ideal for all services. Therefore, the network may desire to change the DRX configuration depending on the services that the mobile device is receiving to improve network performance and/or user experience. To change the DRX configuration, the network sends the new DRX parameters to the mobile device in a radio resource control (RRC) message. The mobile device applies the new DRX parameters and sends a response message to the network indicating that the reconfiguration is complete, at which time the network applies the new DRX parameters. Thus, changing the DRX configuration while the mobile device is connected can result in a connection failure if the mobile device commits to a new DRX configuration but there is a delay in sending the response message from the mobile device.